One-step coprecipitation synthesis of Cl− intercalated Fe3O4@SiO2 @MgAl LDH nanocomposites with excellent adsorption performance toward three dyes

Abstract

A magnetic Cl−-intercalated Fe3O4@SiO2@MgAl-Cl− LDH nanocomposite has been successfully synthesized by modified one-step salt-assisted coprecipitation process. The Fe3O4@SiO2@MgAl-Cl− LDH nanocomposite was characterized by FTIR, XRD, XPS, SEM, HRTEM, BET and VSM. The results showed that the Fe3O4@SiO2@MgAl-Cl− LDH particles possessed core (Fe3O4@SiO2) shell (Cl− -LDH) structures and magnetic properties, and Cl− anions were successfully introduced into LDH interlayers. The unique intercalated structure with week interlayer interaction of Fe3O4@SiO2@MgAl-Cl− LDH provide efficient adsorption of methyl orange (MO), Congo red (CR) and methyl blue (MB), leading to its superior performance with much higher uptake capability with the maximum adsorption capacity of MO, CR and MB reaching 733 mg·g−1, 910 mg·g−1 and 385 mg·g−1, respectively. The adsorption process could be well described by pseudo-second-order model for MO, CR and MB. The experimental data of MO and CR could be fitted better with Freundlich model, while that of MB were fitted better with Langmuir model. The adsorption process was spontaneous and exothermic for MO and MB, while spontaneous and endothermic for CR. Moreover, the adsorbent exhibits excellent stability and reusability in the regeneration cycle, and a process called ‘‘post-processing step” is proposed to effectively improve the dye removal ability of the adsorbent in reuse. This study puts forward a new thought for the development of high-performance LDH adsorbents with mesoporous and Cl− intercalation structure for the efficient and rapid removal of dyes.